Compositions and methods for parallel processing of electrode film mixtures

ABSTRACT

Materials and methods for preparing electrode film mixtures and electrode films including reduced damage bulk active materials are provided. In a first aspect, a method for preparing an electrode film mixture for an energy storage device is provided, comprising providing an initial binder mixture comprising a first binder and a first active material, processing the initial binder mixture under high shear to form a secondary binder mixture, and nondestructively mixing the secondary binder mixture with a second portion of active materials to form an electrode film mixture.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference in their entirety under37 CFR 1.57. This application claims the benefit of U.S. ProvisionalPatent Application No. 62/580,931, filed Nov. 2, 2017, entitled“COMPOSITIONS AND METHODS FOR PARALLEL PROCESSING OF ELECTRODE FILMMIXTURES.”

BACKGROUND Field of the Invention

The present invention relates generally to energy storage devices, andspecifically to materials and methods for parallel processing ofmixtures of electrode active materials and electrode binders.

Description of the Related Art

Electrical energy storage cells are widely used to provide power toelectronic, electromechanical, electrochemical, and other usefuldevices. Such cells include batteries such as primary chemical cells andsecondary (rechargeable) cells, fuel cells, and various species ofcapacitors, including ultracapacitors. Increasing the cycle life ofenergy storage devices, including capacitors and batteries, would bedesirable for enhancing energy storage, increasing power capability, andbroadening real-world use cases.

SUMMARY

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention aredescribed herein. Not all such objects or advantages may be achieved inany particular embodiment of the invention. Thus, for example, thoseskilled in the art will recognize that the invention may be embodied orcarried out in a manner that achieves or optimizes one advantage orgroup of advantages as taught herein without necessarily achieving otherobjects or advantages as may be taught or suggested herein.

In a first aspect, a method for preparing an electrode film mixture foran energy storage device is provided, comprising providing an initialbinder mixture comprising a first binder and a first active material,processing the initial binder mixture under high shear to form asecondary parallel processed binder mixture, and nondestructively mixingthe secondary binder mixture with a second portion of active materialsto form an electrode film mixture.

In another aspect, a parallel processing method for preparing anelectrode film is provided. In some embodiments, the method includesproviding an initial binder mixture comprising a first binder and afirst active material. In some embodiments, the method includesprocessing the initial binder mixture under high shear to form asecondary binder mixture. In some embodiments, the method includesforming an electrode film mixture by mixing the secondary binder mixturewith a second active material by a first nondestructive mixing process.In some embodiments, the method includes forming an electrode film fromthe electrode film mixture, wherein the electrode film is afree-standing film.

In some embodiments, mixing the secondary binder mixture with the secondactive material by the first nondestructive mixing process comprisesmixing at least one of a lower pressure, lower velocity, and faster feedrate than the processing under high shear step. In some embodiments, thefirst binder and the first active material are mixed by a secondnondestructive mixing process to form the initial binder mixture priorto providing the initial binder mixture. In some embodiments, at leastone of the first and the second nondestructive mixing processes is anacoustic mixing process. In some embodiments, mixing comprises mixingthe binder mixture with an active material mixture, the active materialmixture comprising the second active material.

In some embodiments, the active material mixture further comprises asecond binder. In some embodiments, the mass ratio of the first activematerial to the first binder is between about 1:1 to about 4:1 byweight. In some embodiments, the second active material comprises atreated surface. In some embodiments, the second active material withinthe electrode film comprises active material particle surfaces that arepristine. In some embodiments, the combined D₅₀ particle sizedistribution of a total active material, including the first and secondactive materials, in the electrode film mixture is at least about 6 μm.In some embodiments, the electrode film mixture is not exposed to a highshear process before being formed into the electrode film.

In another aspect, an electrode film for an energy storage device isprovided. In some embodiments, the electrode film includes an activematerial comprising active material particles, wherein the D₅₀ sizedistribution of a total of the active material particles is at leastabout 6 μm. In some embodiments, the electrode film includes a binder.In some embodiments, the electrode film is a free-standing film.

In another aspect, an energy storage device is provided. In someembodiments, the energy storage device includes an anode comprising anelectrode film, wherein the electrode film comprises an active materialcomprising graphite, and a binder comprising PTFE. In some embodiments,the energy storage device includes a cathode. In some embodiments, theenergy storage device includes a separator. In some embodiments, theenergy storage device includes an electrolyte. In some embodiments, theenergy storage device has a first cycle efficiency of greater than about85%.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments of the presentinvention will become readily apparent to those skilled in the art fromthe following detailed description of the preferred embodiments havingreference to the attached figures, the invention not being limited toany particular preferred embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an embodiment of an energy storage device.

FIG. 2 provides a flow chart for parallel preparation of electrode filmmixtures.

FIG. 3 provides a particle size analysis of graphite particles afterbeing jet milled at 40/40 psi with various feed rates.

FIGS. 4A-4C depict SEM images of a 4:1 graphite:PTFE binder mixtureafter Resodyn mixing (FIG. 4A), after jet milling at 80 psi (FIG. 4B),and after calender rolling (FIG. 4C).

FIG. 5 provides a graph showing the first cycle electrochemical voltageprofile for three lithium ion batteries with different electrodefabricated under serial and parallel processing conditions. Efficienciesof the batteries were determined by the change in voltage between theinitial lithiation and delithiation curves.

FIG. 6 provides a graph showing the mechanical strength ofself-supporting electrode films made with 2:1, 3:1, 4:1 graphite:PTFEbinder mixture ratios and including 3% PTFE fabricated by parallelprocesses.

FIG. 7 provides a graph showing the first cycle electrochemicalefficiency of energy storage devices with electrode films made with 2:1,3:1, and 4:1 graphite:PTFE binder mixture ratios and including 3% PTFEfabricated by parallel processes.

FIGS. 8A and 8B provide electrochemical first cycle profiles of energystorage devices with electrode films made with 2:1 graphite:PTFE bindermixture ratios including 1.5% PTFE and 3% PTFE fabricated by parallelprocesses and calendar rolled. FIG. 8A shows an example first cycleefficiency for a 1.5% PTFE film of 88.7%, and FIG. 8B shows an examplefirst cycle efficiency for another 1.5% PTFE film of 91.0%.

FIG. 9 provides an example of an implementation of a parallel processingscheme to form an electrode film.

FIG. 10 provides a chart showing D₅₀ particle size distributions ofgraphite resulting from a conventional process (“serial process”), froma parallel process as provided herein (“parallel process”), and withrespect to unprocessed pristine graphite.

DETAILED DESCRIPTION Definitions

As used herein, the terms “battery” and “capacitor” are to be giventheir ordinary and customary meanings to a person of ordinary skill inthe art. The terms “battery” and “capacitor” are nonexclusive of eachother. A capacitor or battery can refer to a single electrochemical cellthat may be operated alone, or operated as a component of a multi-cellsystem.

As used herein, the voltage of an energy storage device is the operatingvoltage for a single battery or capacitor cell. Voltage may exceed therated voltage or be below the rated voltage under load, or according tomanufacturing tolerances.

As provided herein, a “self-supporting” electrode film or active layeris an electrode film or layer that incorporates binder matrix structuressufficient to support the film or layer and maintain its shape such thatthe electrode film or layer can be free-standing. When incorporated inan energy storage device, a self-supporting electrode film or activelayer is one that incorporates such binder matrix structures. Generally,and depending on the methods employed, such electrode films or activelayers are strong enough to be employed in energy storage devicefabrication processes without any outside supporting elements, such as acurrent collector or other film. For example, a “self-supporting”electrode film can have sufficient strength to be rolled, handled, andunrolled within an electrode fabrication process without othersupporting elements.

As provided herein, a “solvent-free” electrode film is an electrode filmthat contains no detectable processing solvents, processing solventresidues, or processing solvent impurities. Processing solvents ortraditional solvents include organic solvents. A dry electrode film,such as a cathode electrode film or an anode electrode film, may besolvent-free.

A “wet” electrode or “wet process” electrode is an electrode prepared byat least one step involving a slurry of active material(s), binder(s),and processing solvents, processing solvent residues, and/or processingsolvent impurities. A wet electrode may optionally include additive(s).

As provided herein, a “nondestructive” process is a process in which anelectrode active material, including the surface of the electrode activematerial, is not substantially modified during the process. Thus, theanalytical characteristics and/or performance in an application, such asincorporation in an energy storage device, of the active material, areidentical or nearly identical to those which have not undergone theprocess. For example, a coating on the active material may beundisturbed or substantially undisturbed during the process. Anonlimiting example of a nondestructive process is “nondestructivelymixing or blending,” or jet milling at a reduced pressure, increasedfeed rate, decreased velocity (e.g., blender speed), and/or change inother process parameter(s) such that the shear imparted upon an activematerial remains below a threshold at which the analyticalcharacteristics and/or performance of the active material would beadversely affected, when implemented into an energy storage device. A“nondestructive” process can be distinguished from a high shear processwhich substantially modifies an electrode active material, such as thesurface of an electrode active material, and substantially affects theanalytical characteristics and/or the performance of the activematerial. For example, high shear blending or jet milling can havedetrimental effects on the surface of an electrode active material. Ahigh shear process may be implemented, at the detriment to the activematerial surface characteristics, to provide other benefits, such asfibrillization of binder material, or otherwise forming a binder/activematerial matrix to assist in forming a self-supporting electrode film.Embodiments herein provide similar benefits, while avoiding thedetrimental effects of excessive use of high shear processes. Ingeneral, the nondestructive processes herein are performed at one ormore of a higher feed rate, lower velocity, and/or lower pressure,resulting in a lower shear process than the more destructive processesthat will otherwise substantially modify an electrode active material,and thus affect performance.

As provided herein, “binder loading” refers to the mass of binderrelative to the mass of the final electrode film mixture. Binder loadingcan be expressed with respect to a single binder, or a “total binderloading” which is the sum of the mass of all types of binders relativeto the mass of the final electrode film mixture.

DESCRIPTION

Under various operating conditions, a number of deleterious processesmay take place at the surfaces of active materials. These processes mayresult in a reduction in performance over the life of the device, andmay result in outright cell failure. Over the life of an energy storagedevice, deterioration of device performance may manifest as reducedstorage capacity, capacitance fade, increased equivalent seriesresistance (ESR) of the device, self-discharge, pseudocapacity, and/orgas formation. Damaged electrode active materials are thought tocontribute to these processes. Steps employed in typical, single path orserial dry electrode fabrication techniques generally include high shearand/or high pressure processing steps performed on all the dry electrodebinder and active materials. Such high shear processing may damage theelectrode active materials, and thus contribute to these aforementionednegative effects, once this raw material is formed into an electrodewithin an energy storage device. Thus, there is a need for electrodefilm mixtures and processes that include reduced damage bulk activematerials.

Provided herein are various embodiments incorporating materials andmethods by which parallel processes can be implemented for formingelectrode film mixtures, electrode films, and energy storage devicesincorporating the electrode films. An energy storage device as providedherein may be fabricated from an electrode film mixture as providedherein. Further, an energy storage device as provided herein may beconstructed by a method as provided herein.

In typical dry electrode fabrication procedures, at least two problemscould be identified. First, significant damage was done to the activematerial particles during high shear mixing methods such as jet millprocessing, as evidenced by a reduction in particle size during jet millprocessing. In a simplistic representation, it is believed that smallerparticle sizes correspond with more damaged particles. Thus, high shearprocessing may damage active material particles. Without wishing to belimited by theory, it is thought that such damage may contribute toadditional, undesired, reactions on the surfaces of active materials,for example, by revealing fresh and/or uncoated graphite step surfaces.Second, binders, while necessary for film cohesion, do not contribute toenergy storage. These problems may contribute to reduced energy and/orpower performance in an energy storage device. However, high shearprocessing is needed to disperse PTFE particles in a manner suitable forforming a self-supporting, processable dry electrode film. Thus,improved processing methods for dry electrode films are needed.

The materials and methods provided herein address the issues notedabove. The processes provided herein generally proceed by a parallelprocess including at least two steps. First, a binder mixture isprepared. The binder mixture generally includes a first binder suitablefor providing structure to a dry processed electrode film, and amaterial suitable for adhering to the first binder. The first binder maybe a fibrillizable binder, and may comprise PTFE. The material suitablefor adhering to the first binder may be an active electrode material.The components of the first binder mixture are first combined and mixedthrough a lower shear, nondestructive process, as described herein, andthen subjected to a higher shear process, such as milling. Second, abulk active material mixture is prepared. The active material mixturegenerally includes the bulk active materials that, upon processing andfabrication, will comprise the electrode film. The active materialmixture may include at least one active material, and optionally one ormore binders. Finally, the binder mixture may be combined with theactive material mixture. The binder mixture and bulk active materialmixtures may be mixed in a nondestructive process to form an electrodefilm mixture. The active material in the binder mixture and the activematerial in the bulk active material may be the same. Optionally, anelectrode film can then be formed from the electrode film mixture, forexample, by pressing or calendering. Advantageously, the use of anactive material-binder parallel process may improve the characteristicsof the final electrode film by only subjecting a small percentage of theoverall active material through damaging high shear and/or high pressuremixing procedures.

Unexpectedly, it was discovered that the parallel processing methodsprovided herein may more efficiently utilize the binder available. Thus,some electrode films fabricated as described herein were stronger thanthose fabricated using typical dry electrode methods. Without wishing tobe limited by theory, it is thought that the fibrillizable binder mayachieve better dispersion in a parallel process as described herein.Also surprisingly, some electrodes fabricated using the materials andmethods provided herein displayed significantly improved performance.

The parallel processes and electrode film forming processes arecompatible with dry electrode fabrication technology. In someembodiments, no solvents are used in any stage of the parallel processnor in the electrode film fabrication.

The present disclosure allows nondestructively processed activematerials, for example undamaged and/or pristine surfaces of activematerial particulates, to be incorporated into an electrode filmmixture. Undamaged and/or pristine active materials may includematerials with substantially similar surface area distributions, surfacechemical reactivates and/or surface chemical compositions to thematerials as purchased commercially and/or prior to a process that mightalter these physical characteristics of active materials. Thus, reducedsurface degradation bulk active material(s) are provided.

Polymer binders, and in particular fluorinated polymer binders such aspolytetrafluoroethylene (PTFE), are binders commonly used in electrodes.Some such binders can undergo fibrillization and enable themanufacturing of self-standing films without the aid of a solvent.Manufacturing such films requires physical processing of the bulk binderto create fine particles, which can undergo fibrillization to create amatrix suitable for providing structure to the electrode film.Typically, this binder processing has been performed by a milling orblending operation at high pressure and under high shear forces, and inthe presence of the electrode active material(s) to form an electrodefilm mixture. The forces applied in processing the binder may alter theform of the active material(s), and may damage the surface of the activematerial(s). For example, the particles of active material(s) may break,fuse, strip, or be chemically altered during such processing.

Such active materials as incorporated in energy storage deviceelectrodes may have coated and/or treated surfaces. For example, carbonmaterials, and in particular graphitic carbon, may be coated withamorphous carbon. Alternatively or in addition, graphitic carbon may besurface treated to reduce functional groups, and specificallyhydrogen-containing functional groups, nitrogen-containing functionalgroups, and/or oxygen-containing functional groups. Without wishing tobe limited by theory, it is thought that the composition of the activematerial surface affects degradation processes within the energy storagedevice, e.g., of the electrolyte and impurities therein, and alsoaffects formation of a surface-electrolyte interphase (SEI) layer.Surface-treated active materials may exhibit better performance in anenergy storage device electrode compared to active material(s) havinguntreated surfaces. Better performance may be due to, for example,reduced fissure formation and/or cracking, reduced separation of activematerial(s) from a current collector, reduced decomposition of theelectrolyte, and/or reduced gassing.

As noted above, processing of a mixture of binder and active material(s)may break the particles of active material(s), and this may expose new,uncoated and/or untreated surfaces of the active material(s). The newlyexposed surfaces of the active material(s) may exhibit unfavorablesurface characteristics that lead to degradation processes. Thus, theoverall performance of the device may be reduced compared to a deviceincorporating coated and/or surface treated, for example, pristine,active material(s). Thus, disclosed herein in some embodiments arematerials and methods providing active material(s) incurring reducedsurface damage during fabrication. Further disclosed herein in someembodiments are nondestructive methods for dry electrode fabrication.Certain embodiments of energy storage devices provided herein mayprovide reduced surface damage graphitic carbon following processing. Inparticular, self-supporting electrode films including reduced damageactive material(s) are provided.

Advantageously, and unexpectedly, it has been discovered that electrodefilms formed using parallel processes as described herein may toleratelower binder loading than those formed using typical dry electrode filmforming processes. Without wishing to be limited by theory, it isthought that the use of a parallel process as described herein maybetter disperse the polymer binder compared to a typical dry electrodeprocess. Thus, in some embodiments, a binder matrix sufficient toprovide a self-supporting electrode film can be provided with loweroverall binder loading compared to a typical dry electrode process.

An electrode film formed using a parallel process as described hereinmay advantageously exhibit improved performance relative to one formedusing typical dry electrode film forming processes. In particular, thefirst cycle efficiency of a lithium ion battery including at least oneelectrode prepared using a parallel process as provided herein may beimproved. For example, first cycle columbic efficiency duringelectrochemical cycling may be improved. Without wishing to be limitedby theory, it is believed that the improvement can be attributed to thereduced surface damage in the bulk active material, and in appropriatecircumstances to reduced binder loading. In some embodiments, anelectrode film includes reduced binder loading compared to onefabricated using a typical dry electrode process, while mechanicalstrength of the electrode film is maintained.

The materials and methods provided herein can be implemented in variousenergy storage devices. As provided herein, an energy storage device canbe a capacitor, a lithium ion capacitor (LIC), an ultracapacitor, abattery, or a hybrid energy storage device and/or a hybrid cell,combining aspects of two or more of the foregoing. In some embodiments,the device is a battery. The energy storage device can be characterizedby an operating voltage. In some embodiments, an energy storage devicedescribed herein can have an operating voltage of about 0 V to about 4.5V. In further embodiments, the operating voltage can be about 2.7 V toabout 4.2 V, about 3.0 to about 4.2 V, or any values therebetween.

An energy storage device as provided herein includes one or moreelectrodes. An electrode generally includes an electrode film and acurrent collector. The electrode film can be formed from a mixture ofone or more binders and one or more active electrode material(s). Itwill be understood that a parallel processed electrode binder, and anelectrode including a parallel processed binder provided herein, can beused in various embodiments with any of a number of energy storagedevices and systems, such as one or more batteries, capacitors,capacitor-battery hybrids, fuel cells, or other energy storage systemsor devices, and combinations thereof. In some embodiments, an electrodefilm mixture, and an electrode fabricating from an electrode filmmixture described herein may be a component of a lithium ion capacitor,a lithium ion battery, an ultracapacitor, or a hybrid energy storagedevice combining aspects of two or more of the foregoing.

An energy storage device as provided herein can be of any suitableconfiguration, for example planar, spirally wound, button shaped, orpouch. An energy storage device as provided herein can be a component ofa system, for example, a power generation system, an uninterruptiblepower source systems (UPS), a photo voltaic power generation system, anenergy recovery system for use in, for example, industrial machineryand/or transportation. An energy storage device as provided herein maybe used to power various electronic device and/or motor vehicles,including hybrid electric vehicles (HEV), plug-in hybrid electricvehicles (PHEV), and/or electric vehicles (EV).

An energy storage device described herein may advantageously becharacterized by reduced rise in equivalent series resistance over thelife of the device, which may provide a device with increased powerdensity over the life of the device. In some embodiments, energy storagedevices described herein may be characterized by reduced loss ofcapacity over the life of the device. Further improvements that may berealized in various embodiments include improved cycling performance,including improved storage stability during cycling, and reducedcapacity fade.

FIG. 1 shows a side cross-sectional schematic view of an example of anenergy storage device 100 fabricated using an electrode film parallelprocess described herein. The energy storage device 100 may beclassified as, for example, a capacitor, a battery, a capacitor-batteryhybrid, or a fuel cell.

The device can have a first electrode 102, a second electrode 104, and aseparator 106 positioned between the first electrode 102 and secondelectrode 104. The first electrode 102 and the second electrode 104 maybe placed adjacent to respective opposing surfaces of the separator 106.The energy storage device 100 may include an electrolyte 118 tofacilitate ionic communication between the electrodes 102, 104 of theenergy storage device 100. For example, the electrolyte 118 may be incontact with the first electrode 102, the second electrode 104 and theseparator 106. The electrolyte 118, the first electrode 102, the secondelectrode 104, and the separator 106 may be received within an energystorage device housing 120. One or more of the first electrode 102, thesecond electrode 104, and the separator 106, or constituent thereof, maycomprise porous material. The pores within the porous material canprovide containment for and/or increased surface area for reactivitywith an electrolyte 118 within the housing 120. The energy storagedevice housing 120 may be sealed around the first electrode 102, thesecond electrode 104 and the separator 106, and may be physically sealedfrom the surrounding environment.

In some embodiments, the first electrode 102 can be an anode (the“negative electrode”) and the second electrode 104 can be the cathode(the “positive electrode”). The separator 106 can be configured toelectrically insulate two electrodes adjacent to opposing sides of theseparator 106, such as the first electrode 102 and the second electrode104, while permitting ionic communication between the two adjacentelectrodes. The separator 106 can comprise a suitable porous,electrically insulating material. In some embodiments, the separator 106can comprise a polymeric material. For example, the separator 106 cancomprise a cellulosic material (e.g., paper), a polyethylene (PE)material, a polypropylene (PP) material, and/or a polyethylene andpolypropylene material.

Generally, the first electrode 102 and second electrode 104 eachcomprise a current collector and an electrode film. Electrodes 102 and104 comprise electrode films 112 and 114, respectively. Electrode films112 and 114 can have any suitable shape, size and thickness. Forexample, the electrode films can have a thickness of about 30 microns(μm) to about 250 microns, for example, about 50 microns, about 100microns, about 150 microns, about 200 microns, about 250 microns, or anyrange of values therebetween, or other thicknesses. The electrode filmscan comprise one or more parallel-processed binder materials. In someembodiments, electrode films 112 and 114, can include parallel-processedbinder mixtures comprising binder material and an active material. Insome embodiments, the active material can be a carbon based material ora battery material. In some embodiments, an active material can includea lithium metal oxide, sulfur carbon composite and/or a lithium sulfide.In some embodiments, active material may include lithium nickelmanganese cobalt oxide (NMC), lithium manganese oxide (LMO), lithiumiron phosphate (LFP), lithium cobalt oxide (LCO), lithium titanate(LTO), and/or lithium nickel cobalt aluminum oxide (NCA). In someembodiments, the active material may include other material describedherein.

The at least one active material may include one or more carbonmaterials. The carbon materials may be selected from, for example,graphitic material, graphite, graphene-containing materials, hardcarbon, soft carbon, carbon nanotubes, porous carbon, conductive carbon,or a combination thereof. Activated carbon can be derived from a steamprocess or an acid/etching process. In some embodiments, the graphiticmaterial can be a surface treated material. In some embodiments, theporous carbon can comprise activated carbon. In some embodiments, theporous carbon can comprise hierarchically structured carbon. In someembodiments, the porous carbon can include structured carbon nanotubes,structured carbon nanowires and/or structured carbon nanosheets. In someembodiments, the porous carbon can include graphene sheets. In someembodiments, the porous carbon can be a surface treated carbon. Inpreferred embodiments, the active material comprises, consistsessentially of, or consists of graphite.

The first electrode film 112 and/or the second electrode film 114 mayalso include parallel-processed binders as provided herein. In someembodiments, the binder can include one or more polymers. In someembodiments, the binder can include one or more fibrillizable bindercomponents. The binder component may be fibrillized to provide aplurality of fibrils, the fibrils desired mechanical support for one ormore other components of the film. It is thought that a matrix, lattice,or web of fibrils can be formed to provide mechanical structure to theelectrode film. In some embodiments, a binder component can include oneor more of a variety of suitable fibrillizable polymeric materials.

Generally, the electrode films described herein can be fabricated usinga modified dry fabrication process. For example, some steps providedherein may be as described in U.S. Patent Publication No. 2005/0266298and U.S. Patent Publication No. 2006/0146479. These, and any otherreferences to extrinsic documents herein, are hereby incorporated byreference in their entirety. As used herein, a dry fabrication processcan refer to a process in which no or substantially no solvents are usedin the formation of an electrode film. For example, components of theelectrode film, including carbon materials and binders, may comprise dryparticles. The dry particles for forming the electrode film may becombined to provide a dry particle electrode film mixture. In someembodiments, the electrode film may be formed from the dry particleelectrode film mixture such that weight percentages of the components ofthe electrode film and weight percentages of the components of the dryparticles electrode film mixture are substantially the same. In someembodiments, the electrode film formed from the dry particle electrodefilm mixture using the dry fabrication process may be free from, orsubstantially free from, any processing additives such as solvents andsolvent residues resulting therefrom. In some embodiments, the resultingelectrode films are self-supporting electrode films formed using the dryprocess from the dry particle mixture. In some embodiments, theresulting electrode films are free-standing electrode films formed usingthe dry process from the dry particle mixture. A process for forming anelectrode film can include fibrillizing the fibrillizable bindercomponent(s) such that the electrode film comprises fibrillized binder.In further embodiments, a free-standing electrode film may be formed inthe absence of a current collector. In still further embodiments, anelectrode film may comprise a fibrillized polymer matrix such that theelectrode film is self-supporting.

As shown in FIG. 1, the first electrode 102 and the second electrode 104include a first current collector 108 in contact with first electrodefilm 112, and a second current collector 110 in contact with the secondelectrode film 114, respectively. The first current collector 108 andthe second current collector 110 may facilitate electrical couplingbetween each corresponding electrode film and an external electricalcircuit (not shown). The first current collector 108 and/or the secondcurrent collector 110 can comprise one or more electrically conductivematerials, and have any suitable shape and size selected to facilitatetransfer of electrical charge between the corresponding electrode and anexternal circuit. For example, a current collector can include ametallic material, such as a material comprising aluminum, nickel,copper, rhenium, niobium, tantalum, and noble metals such as silver,gold, platinum, palladium, rhodium, osmium, iridium and alloys andcombinations of the foregoing. For example, the first current collector108 and/or the second current collector 110 can comprise an aluminumfoil. The aluminum foil can have a rectangular or substantiallyrectangular shape sized to provide transfer of electrical charge betweenthe corresponding electrode and an external electrical circuit.

In some embodiments, the energy storage device 100 is a lithium ionbattery or hybrid energy storage device including a cathode comprisingan active material. In some embodiments, the lithium ion battery isconfigured to operate at about 2.5 to 4.5 V, or 2.7 to 4.2 V.

In some embodiments, an energy storage device is configured to operateat 3 volts or greater. In further embodiments, an energy storage deviceis configured to operate at 2.7 volts or greater. In some embodiments,an energy storage device is configured for operation at selectedconditions of voltage and temperature. For example, an energy storagedevice can be configured for operation at 50° C., 55° C., 60° C., 65°C., 70° C., 75° C., 80° C., 85° C., 90° C., 95° C., 100° C., or greatertemperatures, or any range of values therebetween. An energy storagedevice can be configured for continual operation at 2.7 V at 60 to 85°C., 2.8 V at 60 to 85° C., 2.9 V at 60 to 85° C., or 3 V at 60 to 85°C., or any selected temperature values therebetween. In someembodiments, the conditions of voltage and temperature are about 2.7 Vand about 85° C., about 2.8 V and about 80° C., about 2.9 V and about75° C., about 3 V and about 70° C., or about 3.1 V and about 65° C.

In some embodiments, secondary electrochemical reactions of theelectrode and/or electrolyte components are reduced in energy storagedevices fabricated using a parallel process as described herein.

Technologies described herein may be used separately or in combinationin an energy storage device to enable operation under the selectedconditions.

Lithium Ion Energy Storage Device

In some embodiments, energy storage device 100 can be a lithium ionenergy storage device such as a lithium ion capacitor, a lithium ionbattery, or a hybrid lithium ion device. In some embodiments, anelectrode film of a lithium ion energy storage device electrode cancomprise one or more active materials, and a fibrillized binder matrixas provided herein. An electrode film may be fabricated by a parallelprocessing method described herein.

In some embodiments, an electrode film of a lithium ion energy storagedevice can comprise an anode active material. Anode active materials cancomprise, for example, an insertion material (such as carbon, graphite,and/or graphene), an alloying/dealloying material (such as silicon,silicon oxide, tin, and/or tin oxide), a metal alloy or compound (suchas Si—Al, and/or Si—Sn), and/or a conversion material (such as manganeseoxide, molybdenum oxide, nickel oxide, and/or copper oxide). The anodeactive materials can be used alone or mixed together to form multi-phasematerials (such as Si—C, Sn—C, SiOx-C, SnOx-C, Si—Sn, Si-SiOx, Sn-SnOx,Si-SiOx-C, Sn-SnOx-C, Si—Sn—C, SiOx-SnOx-C, Si-SiOx-Sn, orSn-SiOx-SnOx.).

In some embodiments, an electrode film of a lithium ion energy storagedevice can comprise active cathode material. In some embodiments, theelectrode film may further comprise a binder, and optionally a porouscarbon material, and optionally a conductive additive. In someembodiments, the conductive additive may comprise a conductive carbonadditive, such as carbon black. In some embodiments, the porous carbonmaterial may comprise activated carbon. In some embodiments, the cathodeactive material can include a lithium metal oxide and/or a lithiumsulfide. In some embodiments, the cathode active material may includelithium nickel manganese cobalt oxide (NMC), lithium manganese oxide(LMO), lithium iron phosphate (LFP), lithium cobalt oxide (LCO), lithiumtitanate (LTO), and/or lithium nickel cobalt aluminum oxide (NCA). Thecathode active material can comprise sulfur or a material includingsulfur, such as lithium sulfide (Li2S), or other sulfur-based materials,or a mixture thereof. In some embodiments, the cathode film comprises asulfur or a material including sulfur active material at a concentrationof at least 50 wt %. In some embodiments, the cathode film comprising asulfur or a material including sulfur active material has an arealcapacity of at least 10 mAh/cm². In some embodiments, the cathode filmcomprising a sulfur or a material including sulfur active material hasan electrode film density of 1 g/cm³. In some embodiments, the cathodefilm comprising a sulfur or a material including sulfur active materialfurther comprises a binder. In some embodiments, the binder of thecathode film comprising a sulfur or a material including sulfur activematerial is selected from polytetrafluoroethylene (PTFE), polyvinylidenefluoride (PVDF), poly(ethylene oxide) (PEO), polyethylene (PE),polyacrylic acid (PAA), gelatin, other thermoplastics, or anycombination thereof.

In some embodiments, a cathode electrode film of a lithium ion batteryor hybrid energy storage device can include about 70 weight % to about98 weight % of the active material, including about 70 weight % to about96 weight %, or about 70 weight % to about 88 weight %. In someembodiments, the cathode electrode film can comprise up to about 10weight % of the porous carbon material, including up to about 5 weight%, or about 1 weight % to about 5 weight %. In some embodiments, thecathode electrode film comprises up to about 5 weight %, including about1 weight % to about 3 weight %, of the conductive additive. In someembodiments, the cathode electrode film comprises up to about 20 weight% of the binder, for example, about 1.5 weight % to 10 weight %, about1.5 weight % to 5 weight %, or about 1.5 weight % to 3 weight %. In someembodiments, the cathode electrode film comprises about 1.5 weight % toabout 3 weight % binder.

In some embodiments, an anode electrode film may comprise an activematerial, a binder, and optionally a conductive additive. In someembodiments, the conductive additive may comprise a conductive carbonadditive, such as carbon black. In some embodiments, the active materialof the anode may comprise a graphitic carbon, synthetic graphite,natural graphite, hard carbon, soft carbon, graphene, mesoporous carbon,silicon, silicon oxides, tin, tin oxides, germanium, lithium titanate,mixtures, or composites of the aforementioned materials. In someembodiments, an anode electrode film can include about 80 weight % toabout 98 weight % of the active material, including about 90 weight % toabout 98 weight %, or about 94 weight % to about 97 weight %. In someembodiments, the anode electrode film comprises up to about 5 weight %,including about 1 weight % to about 3 weight %, of the conductiveadditive. In some embodiments, the anode electrode film comprises up toabout 20 weight % of the binder, including about 1.5 weight % to 10weight %, about 1.5 weight % to 5 weight %, or about 3 weight % to 5weight %. In some embodiments, the anode electrode film comprises about4 weight % binder. In some embodiments, the anode film may not include aconductive additive.

In some embodiments, the electrode film of a lithium ion energy storagedevice electrode comprises an electrode film mixture comprising carbonconfigured to reversibly intercalate lithium ions. In some embodiments,the lithium intercalating carbon is selected from a graphitic carbon,graphite, hard carbon, soft carbon and combinations thereof. Forexample, the electrode film of the electrode can include a bindermaterial, one or more of graphitic carbon, graphite, graphene-containingcarbon, hard carbon and soft carbon, and an electrical conductivitypromoting material. In some embodiments, an electrode is mixed withlithium metal and/or lithium ions.

Some embodiments include an electrode, such as an anode and/or acathode, having one or more electrode films comprising a polymericbinder material. The polymeric binder material may be a parallelprocessed binder as provided herein. In some embodiments, the binder maycomprise PTFE and optionally one or more additional binder components.In some embodiments, the binder may comprise one or more polyolefinsand/or co-polymers thereof, and PTFE. In some embodiments, the bindermay comprise a PTFE and one or more of a cellulose, a polyolefin, apolyether, a precursor of polyether, a polysiloxane, co-polymersthereof, and/or admixtures thereof. In some embodiments, the binder caninclude branched polyethers, polyvinylethers, co-polymers thereof,and/or the like. The binder can include co-polymers of polysiloxanes andpolysiloxane, and/or co-polymers of polyether precursors. For example,the binder can include poly(ethylene oxide) (PEO), poly(phenylene oxide)(PPO), polyethylene-block-poly(ethylene glycol), polydimethylsiloxane(PDMS), polydimethylsiloxane-coalkylmethylsiloxane, co-polymers thereof,and/or admixtures thereof. In some embodiments, the one or morepolyolefins can include polyethylene (PE), polypropylene (PP),polyvinylidene fluoride (PVDF), co-polymers thereof, and/or mixturesthereof. The binder can include a cellulose, for example,carboxymethylcellulose (CMC). An admixture of polymers may compriseinterpenetrating networks of the aforementioned polymers or co-polymers.The binder may include a parallel processed binder as provided herein.

The binder may include various suitable ratios of the polymericcomponents. For example, PTFE can be up to about 100 weight % of thebinder, for example, from about 20 weight % to about 95 weight %, about20 weight % to about 90 weight %, including about 20 weight % to about80 weight %, about 30 weight % to about 70 weight %, or about 30 weight% to about 50 weight %. In further embodiments, the binders can comprisePTFE, CMC, and PVDF as binders. In certain embodiments, the electrodefilm can comprise 2 weight % PTFE, 1 weight % CMC, and 1 weight % PVDF.For example, the binder mixture can include a mass of PTFE which is 50%of the total binder content of the electrode film, and 2% of the totalmass of the electrode film.

In further embodiments, the energy storage device 100 is charged with asuitable lithium-containing electrolyte. For example, device 100 caninclude a lithium salt, and a solvent, such as a non-aqueous or organicsolvent. Generally, the lithium salt includes an anion that is redoxstable. In some embodiments, the anion can be monovalent. In someembodiments, a lithium salt can be selected from hexafluorophosphate(LiPF₆), lithium tetrafluoroborate (LiBF₄), lithium perchlorate(LiClO₄), lithium bis(trifluoromethansulfonyl)imide (LiN(SO₂CF₃)₂),lithium trifluoromethansulfonate (LiSO₃CF₃), and combinations thereof.In some embodiments, the electrolyte can include a quaternary ammoniumcation and an anion selected from the group consisting ofhexafluorophosphate, tetrafluoroborate and iodide. In some embodiments,the salt concentration can be about 0.1 mol/L (M) to about 5 M, about0.2 M to about 3 M, or about 0.3 M to about 2 M. In further embodiments,the salt concentration of the electrolyte can be about 0.7 M to about 1M. In certain embodiments, the salt concentration of the electrolyte canbe about 0.2 M, about 0.3 M, about 0.4 M, about 0.5 M, about 0.6 M,about 0.7 M, about 0.8 M. about 0.9 M, about 1 M, about 1.1 M, about 1.2M, or values therebetween.

In some embodiments, an energy storage device provided herein caninclude a liquid solvent. A solvent as provided herein need not dissolveevery component, and need not completely dissolve any component, of theelectrolyte. In further embodiments, the solvent can be an organicsolvent. In some embodiments, a solvent can include one or morefunctional groups selected from carbonates, ethers and/or esters. Insome embodiments, the solvent can comprise a carbonate. In furtherembodiments, the carbonate can be selected from cyclic carbonates suchas, for example, ethylene carbonate (EC), propylene carbonate (PC),vinyl ethylene carbonate (VEC), vinylene carbonate (VC), fluoroethylenecarbonate (FEC), and combinations thereof, or acyclic carbonates suchas, for example, dimethyl carbonate (DMC), diethyl carbonate (DEC),ethyl methyl carbonate (EMC), and combinations thereof. In certainembodiments, the electrolyte can comprise LiPF₆, and one or morecarbonates.

In some embodiments, the active material includes a treated carbonmaterial, where the treated carbon material includes a reduction in anumber of hydrogen-containing functional groups, nitrogen-containingfunctional groups and/or oxygen-containing functional groups, asdescribed in U.S. Patent Publication No. 2014/0098464. For example, thetreated carbon particles can include a reduction in a number of one ormore functional groups on one or more surfaces of the treated carbon,for example about 10% to about 60% reduction in one or more functionalgroups compared to an untreated carbon surface, including about 20% toabout 50%. The treated carbon can include a reduced number ofhydrogen-containing functional groups, nitrogen-containing functionalgroups, and/or oxygen-containing functional groups. In some embodiments,the treated carbon material comprises functional groups less than about1% of which contain hydrogen, including less than about 0.5%. In someembodiments, the treated carbon material comprises functional groupsless than about 0.5% of which contains nitrogen, including less thanabout 0.1%. In some embodiments, the treated carbon material comprisesfunctional groups less than about 5% of which contains oxygen, includingless than about 3%. In further embodiments, the treated carbon materialcomprises about 30% fewer hydrogen-containing functional groups than anuntreated carbon material.

Electrode Films and Electrode Film Mixtures Fabricated by ParallelBinder Processing

Provided herein are compositions and methods for electrode filmscharacterized by reduced surface damage to active materials. Parallelprocessing of binder and active material advantageously has been foundto allow only a subset of active material to be submitted to damaginghigh shear and/or high pressure processing. Some active materialparticles having an undamaged and/or pristine surface can be added toand mixed with the binder mixture to form an electrode film mixture.Thus, at least a portion of the active material in the electrode filmmixture may have favorable surface characteristics, and the bulkelectrode film formed therefrom may exhibit improved performance.Additionally, it was found that some electrode films formed usingparallel processing methods as provided herein enjoyed unexpectedadvantages in efficiency and/or film strength.

Generally, a binder mixture is prepared by mixing a binder material witha portion of the active material(s) constituting the electrode filmmixture to form a binder mixture. Generally, the mixing of activematerial and binder can be by a method provided herein, or by anysuitable method. The mixing may be by a nondestructive process. Thenondestructive mixing may comprise blending, tumbling, or acousticmixing. It was found that acoustic mixing generally provided the mostefficient mixing with the least damage to the active material particles.

The active material and binder can be processed by a high shear and/orhigh pressure process to form a binder mixture. The high shear and/orhigh pressure process may include jet-milling or blending. Theprocessing time and/or feed rate generally will have an effect on thefinal particle size of the binder and/or active material(s). Forexample, a longer time and/or slower feed rate may produce smallerparticles. Without wishing to be limited by theory, it is thought thatsmaller particle sizes correspond with more damaged particles, and viceversa. The binder mixture can be combined with additional activematerial(s) and/or binders to form an electrode film mixture suitablefor processing, and in particular calendaring, into an electrode film.In some embodiments, the electrode film so formed is a self-supportingelectrode film.

In various embodiments, the resulting contact between the activematerial and the binder in the binder mixture can be described assticking or clinging. The contact between active material and binderparticle in the binder mixture may be due to for example, intermolecularinteractions such as ionic forces, polar interactions, induced dipoleinteractions, London dispersion forces, and/or surface forces. Theactive material particles may adhere to the PTFE particles such thatagglomerations are formed. Some binder particles may be completelyencased within such agglomerations. In some embodiments, the weightpercent portion of active material(s) in the binder mixture may beabout, at least about, or at most about, 1%, 2%, 3%, 4%, 5%, 10%, 15%,or 20% of the total active material in the electrode film mixture orelectrode film, or any range of values therebetween. In someembodiments, the weight percent portion of one or more binder materialsin the binder mixture may be about, at least about, or at most about,100%, 99%, 98%, 95%, 90%, 80%, 70%, 60%, 50% or 40% of the total binderin the electrode film mixture or electrode film, or any range of valuestherebetween.

The active material(s) combined with binder for processing into a bindermixture may generally be any active material(s) suitable for includingin an electrode film. The active material(s) may include, for example, acarbon material as provided herein. The carbon material may be, forexample, graphitic carbon, graphite, graphene-containing materials,activated carbon, hard carbon, soft carbon, and/or carbon nanotubes. Theactive material(s) may include a battery active material(s) as providedherein. In a preferable embodiment, the active material is graphite.

Generally, the binder combined with active material(s) in the parallelprocess may be a binder suitable for providing structure to an electrodefilm produced by dry electrode fabrication. In some embodiments, thebinder is PTFE and optionally one or more additional binder components.In further embodiments, the binder includes PTFE and a polyolefin,poly(ethylene oxide) (PEO), poly(phenylene oxide) (PPO),polyethylene-block-poly(ethylene glycol), polydimethylsiloxane (PDMS),polydimethylsiloxane-coalkylmethylsiloxane, co-polymers thereof, and/oradmixtures thereof. In some embodiments, the one or more polyolefins caninclude polyethylene (PE), polypropylene (PP), polyvinylidene fluoride(PVDF), co-polymers thereof, and/or mixtures thereof. The binder caninclude a cellulose, for example, carboxymethylcellulose (CMC). Incertain embodiments, the binder comprises, consists essentially, orconsists of PTFE, PVCF, and CMC. In some embodiments, the bindercomprises a fibrillizable polymer.

In some embodiments, the binder mixture may include binder particleshaving selected sizes. In some embodiments, the binder particles in abinder mixture may be about 50 nm, about 100 nm, about 150 nm, about 200nm, about 250 nm, about 300 nm, about 350 nm, about 400 nm, about 450nm, about 500 nm, about 1 μm, about 10 μm, about 50 μm, about 100 μm, orvalues therebetween. In some embodiments, the binder mixture may includeactive material particles having selected sizes. In some embodiments,the active material particles in a binder mixture may on average have alongest dimension of about 4 μm, about 5 μm, about 6 μm, about 7 μm,about 8 μm, about 9 μm, about 10 μm, about 12 μm, about 14 μm, about 16μm, about 18 μm, about 20 μm, about 25 μm, or any range of valuestherebetween. The active material particles may comprise graphite.

The proportions of the first binder material and active materialcombined in the binder mixture can be selected based on any number offactors including the identities of the binder and active materialcomponents, particle sizes, planned processing steps, the desiredmaterial properties of the electrode film such as strength andflexibility, and the desired performance characteristics of theelectrode, for example, of power and/or energy. For example, the massratio of active material(s) to first binder can be about 1:1, about1.5:1, about 2:1, about 3:1, about 4:1, about 5:1, about 6:1, about 8:1,about 10:1, or values therebetween. In preferred embodiments, the massratio of active material(s) to first binder can be about 2:1 to about4:1. The binder mixture may have the same selected mass ratios of activematerial(s) to first binder. Generally, the amount of active material inthe bulk active material mixture may be determined from the amount ofactive material included for processing with the structural binder inthe parallel binder processing, taking into account the total amount ofactive material to be included in the final electrode film mixture. Insome embodiments, the binder mixture is processed in the absence ofprocessing additives.

Advantageously, an electrode film prepared using a parallel processingmethod described herein may be characterized by a greater strength thanan electrode film having the same composition, but prepared byconventional dry electrode techniques. In further embodiments, anelectrode film fabricated using the materials and methods disclosedherein can be characterized by reduced binder loading compared to atypical dry electrode film. In various embodiments, the electrode filmmixture, and/or electrode film, can have a PTFE loading of at most 1%,1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5% by mass, or any range ofvalues therebetween. In certain embodiments, the PTFE loading is about1.5 to about 3%. In further embodiments, the electrode film mixture,and/or electrode film, can have a total binder loading of at most 1%,1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, or 6% by mass, or anyrange of values therebetween. In certain embodiments, the total binderloading is about 1.5 to about 4%. In further embodiments, an electrodefilm prepared by the materials and methods described herein maywithstand certain tensile forces. For example, an electrode film mayincur a tensile force on breaking of about, or greater than about, 0.75Newton (N), about 0.8 N, about 0.9 N, about 1 N, about 1.1 N, about 1.2N, about 1.3 N, about 1.4 N, about 1.5 N, about 1.6 N, about 1.7 N,about 1.8 N, about 1.9 N or about 2 N, or any range of valuestherebetween. In further embodiments, an electrode film prepared by thematerials and methods described herein, may have certain tensilestrengths. For example, an electrode film may have a tensile strength ofabout, or greater than about, 0.25 MPa, about 0.3 MPa, about 0.35 MPa,about 0.4 MPa, about 0.45 MPa, about 0.5 MPa, about 0.55 MPa, about 0.6MPa, about 0.65 MPa or about 0.7 MPa, or any range of valuestherebetween. In some embodiments, the electrode film mixture and/orfree-standing electrode film has a D₅₀ particle size distribution oftotal active material of about, greater than about, or at least about, 6μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm or 10 μm, or anyrange of values therebetween.

In preferred embodiments, the parallel process comprises combining anactive material comprising, consisting essentially, or consisting ofgraphite, and a binder comprising, consisting essentially, or consistingof PTFE to form a binder mixture. In preferred embodiments, a ratio of1:1 to 4:1 of graphite to PTFE by weight is used. The mixture ofgraphite and PTFE can be combined together first by selecting a mixingtechnique that will effectively mix and disperse the two componentswithout damaging the active material(s), for example, the graphiteparticles. In certain embodiments, an electrode fabricated by theprocesses disclosed herein comprises a self-supporting negativeelectrode film (anode), although positive electrode films (cathodes) areanticipated. The processes herein may be beneficial towardsimplementation with a negative electrode, because negative electrodeactive materials may be more susceptible to surface changes duringprocessing.

In some embodiments, the electrode film mixture is subjected to one ormore dry electrode process(es), such as that described in U.S. PatentPublication No. 2015/0072234. In some embodiments, a dry electrode isprovided, wherein the dry electrode is free from processing contaminantssuch as solvents, and wherein the dry electrode is prepared by themethods and materials provided herein.

In further embodiments, an electrode fabricated using the materials andmethods disclosed herein can be characterized by improved performance.The improved performance may be due to, for example, increased firstcycle efficiency. In some embodiments, the first cycle efficiency of anegative electrode fabricated by the materials and methods providedherein is more than or at least about 85%. In further embodiments, thefirst cycle efficiency is about, at least about, or more than about,85%, about 86%, about 87%, about 88%, about 89% about 90%, about 91%,about 92%, about 93%, or any range of values therebetween, and may be,for example, within a range of about 86 to about 93%.

In some embodiments, degradation of PTFE is not an observed failure modeof an energy storage device including an electrode fabricated using thematerials and methods provided herein.

In some embodiments, a method for fabricating an energy storage deviceis provided. In further embodiments, the method comprises selecting abinder, selecting an active material, parallel processing the binder andactive material to form a binder mixture, and combining the bindermixture with additional active materials and optionally with additionalbinders to form an electrode film mixture, optionally fibrillating theelectrode film mixture to form an electrode film, and optionallyapplying the electrode film to a current collector to form an electrode.

FIG. 2 depicts an embodiment of a method 200 for preparing an electrodefilm mixture for use in an energy storage device. In step 205 a suitablebinder is selected. The binder selected may be a binder as providedherein. In some embodiments, the binder selected is a single binder. Insome embodiments, the binder is dry. In some embodiments, the binder isin powder form. In some embodiments, the binder selected is afibrillizable binder, wherein the fibrillizable binder is as providedherein. In preferred embodiments, the binder selected is PTFE. Incertain embodiments, the binder comprises, consists of, or consistsessentially of PTFE or any one of the aforementioned binder materials.

In step 210, a suitable first active material is selected. Generally,the active material is any active material that may be included in anelectrode film of an energy storage device, such as those providedherein. In some embodiments, the active material can comprise a carbonmaterial as provided herein. In further embodiments, the active materialcan be a battery active material, such as a metal oxide or metalsulfide. In preferred embodiments, the active material can comprise,consist essentially of, or consist of a graphitic carbon.

In step 220, the first active material selected in step 210 and bindermaterial selected in step 205 are parallel processed to form a bindermixture. The parallel process can be performed by a high shear and/orhigh pressure process, such as jet milling or blending, to form a bindermixture. The high shear and/or high pressure process may beneficiallydeagglomerate binder particles. Step 220 can include an initial step ofcombining the first active material and binder material in a separatestep prior to being subjected to the high shear and/or high shearprocess. For example, the first active material and binder material canbe combined by any suitable method or methods, such as a non-destructiveprocess. For example, the first active material and binder material canbe combined with an acoustic mixer, such as a Resodyn mixer.

In step 230, the binder mixture is combined with a second activematerial, and optionally additional binder materials. The second activematerial and/or the additional binder materials can be the same ordifferent as the first active material and binder. In some embodiments,the combining can be accomplished by a nondestructive process asprovided herein. For example, the combining can comprise jet-milling atreduced pressure and/or increased feed rate. For example, thejet-milling can be performed at a pressure of 80 psi, 70 psi, 60 psi, 50psi, 40 psi, 30 psi, 20 psi, or values therebetween, at a feed rate of200 g/min, 250 g/min, 300 g/min, 350 g/min, 400 g/min or valuestherebetween. Step 230 can include an initial step of combining thesecond active material and binder mixture in a separate step prior tobeing subjected to the low shear process. For example, the second activematerial and binder mixture can be combined by any suitable method ormethods, such as a non-destructive process. For example, the secondactive material and binder mixture can be combined with an acousticmixer, such as a Resodyn mixer. In some embodiments, the additionalbinders can comprise a binder selected from PTFE, carboxymethylcellulose(CMC), poly(vinylidene fluoride) (PVDF), and combinations thereof. Incertain embodiments, the additional binders are CMC and/or PVDF.

Examples

A binder mixture was prepared by mixing graphite and PTFE first, by anondestructive mixing technique that mixed these two components withoutdamaging the graphite particles. This was achieved by the Resodyn mixer(an acoustic mixer, LabRAM) at 50% power for 5 minutes. Approximately 60Gs of acceleration was needed to disperse the PTFE particles with thegraphite particles. Second, the mixture was then further processed byjet milling at 80 psi grinding pressure and 60 psi feeding pressure witha feed rate of 50 g/min. The resulting powder could be added to otheractive material(s) and/or binders at appropriate proportions as a sourceof PTFE binder.

The binder mixture was then mixed with graphite, carboxymethylcellulose, and polyvinylidene fluoride mixtures using a nondestructiveResodyn acoustic mixer process to create a final mixture. In order toreduce the damage on the graphite particles, a fast feed rate of atleast 300 g/min was needed in a Sturtevant 2-inch diameter micronizer inorder to avoid damage. The feed rate would depend on various factors,but generally a higher feed rate would be expected to correspond withless damage to the graphite particles. FIG. 3 demonstrates the effectsof jet mill feed rate and the resulting particle size to the material(smaller particle sizes are believed to correspond to more damagedparticles, and vice versa). The resulting powder was then processedthrough a calender press to produce a free standing film as in typicaldry electrode fabrication processes.

SEM images of a 4:1 Graphite (Hitachi SMG-A5) to PTFE binder mixture atvarious points of a parallel process is shown in FIG. 4A-4C. The bindermixture after being Resodyned is shown in FIG. 4A. Agglomerated graphiteparticles can be observed in FIG. 4A. It is believed that the graphiteparticles adhere to and coat PTFE particles and the mixing energy in theResodyn mixer was not high enough to break apart these agglomerations.The binder mixture after being jet milled is shown in FIG. 4B. In FIG.4B, small PTFE particles of ˜250 nm in primary particle size can be seento coat the surface of graphite particles. These PTFE particles bind thegraphite particles together. However, little to no fibrillation of thePTFE particles is observed indicating that only dispersion of PTFE canbe achieved with mixing processes. When the binder mixture was calenderrolled for analytical purposes, the mixture formed a very strong butless flexible self-supporting, free standing film. SEM images of thefilm surface shown in FIG. 4C revealed complete fibrillation of most ofthe PTFE particles. Although the binder mixture of FIG. 4C was calenderrolled for analysis, generally the binder mixture would be combined withadditional active materials and/or binders before being calendered intoan electrode film.

A general dry method for preparing a dry electrode, which wasimplemented in the studies described further below with respect to FIGS.5-8B and 10, is as follows: an electrode film mixture of graphitepowder, PTFE, CMC, PVDF were thoroughly mixed. Mixing was varied betweensome of the examples as described. In some examples, the mixing was asingle step, with high shear mixing only, and in others, mixing was aparallel process that includes both non-destructive and high shearmixing, according to some embodiments. The resulting electrode filmmixture was calendered into a free-standing electrode film. Laminationof the electrode film onto a carbon coated copper foil provided a carbonelectrode.

A general method for preparing a lithium-based cell, also implemented inthe studies described further below, was performed as follows: apolyolefin separator was placed on lithium metal, on which theaforementioned carbon electrode was placed to form an electrode stack.An electrolyte comprising 1 molar (1M) lithium hexafluorophosphate(LiPF6) in a carboxylic ester comprising ethylene carbonate (EC) andethyl-methyl carbonate (EMC) at a 3:7 ratio, was applied to theelectrode stack and the combined electrode stack and electrolyte weresealed to form the lithium-based cell.

For comparison of various binder mixtures, first cycle electrochemicalvoltage profiles for three electrode samples, created by the general dryelectrode and lithium-based cell methods previously described, werecollected as shown in FIG. 5. The final electrode films included 94%graphite powder, 3% PTFE and combined 3% CMC/PVDF loadings in the finalelectrode film mixtures each case, to allow for direct comparison and toshow that the improvement over a typical process was due to the binderprocessing. The “Comparative Example” sample is a lithium based cellthat included a dry electrode prepared according to the above dryelectrode and lithium-based cell fabrication technique, wherein theentire electrode film mixture was mixed solely by a high shear process.Sample 1 and Sample 2 are also lithium based cells including a dryelectrode prepared according to the above procedures, but wherein theelectrode films were fabricated from parallel-process electrode filmmixtures by methods provided herein, and wherein a 4:1 graphite-PTFEbinder mixture and a 2:1 graphite-PTFE binder mixture, respectively,were mixed under high shear prior to nondestructive mixing with theremaining active material mixture to form the electrode film mixture,and calender rolling the electrode film mixtures at high temperatures of185° C. to form the free-standing electrode films. As seen in FIG. 5,the “Comparative Example” sample had a first cycle efficiency of only85.0%, whereas the Sample 1 had a first cycle efficiency of 86.6% andthe Sample 2 had the best first cycle efficiency, at 87.8%.

A 20 mm×150 μm electrode film created from a 3:1 graphite-PTFE ratiobinder mixture was also created and produced the strongest film, bytensile force, compared to 20 mm×150 μm electrode films made with 2:1and 4:1 graphite-PTFE ratio binder mixtures, each having 3% PTFEloadings, and created by the general dry electrode methods previouslydescribed without lamination to the current collector and using aparallel process, as shown in FIG. 6. The electrode film created from a2:1 graphite-PTFE ratio binder mixture showed a 1^(st) pass tensileforce of about 1.6 N (tensile strength of about 0.55 MPa) and a 2^(nd)pass tensile force of about 1.4 N (tensile strength of about 0.45 MPa);the electrode film created from a 3:1 graphite-PTFE ratio binder mixtureshowed a 1^(st) pass tensile force of about 1.9 N (tensile strength ofabout 0.65 MPa) and a 2^(nd) pass tensile force of about 1.7 N (tensilestrength of about 0.55 MPa); and electrode film created from a 4:1graphite-PTFE ratio binder mixture showed a 1^(st) pass tensile force ofabout 1.5 N (tensile strength of about 0.5 MPa) and a 2^(nd) passtensile force of about 1.5 N (tensile strength of about 0.5 MPa).However, first cycle efficiency of the electrode formed from the 3:1graphite-PTFE ratio binder mixture was less than electrodes made with2:1 and 4:1 graphite-PTFE ratio binder mixtures, as shown in FIG. 7. Theelectrode formed by the general method previously described and from thebinder mixture of 2:1 graphite-PTFE ratio showed a first cycleefficiency of 87.9%; the electrode formed from the binder mixture of 3:1graphite-PTFE ratio showed a first cycle efficiency of 84.1%; and theelectrode formed from the binder mixture of 4:1 graphite-PTFE ratioshowed a first cycle efficiency of 86.6%.

As electrode films made by the parallel processing method describedherein show high tensile forces and strengths, the performance ofelectrode films with lesser PTFE binder loadings were evaluated. Thecurrent optimized first cycle electrochemical performance of a drybattery anode made using a 96% graphite powder, 1.5% PTFE and combined2.5% CMC/PVDF loading in the final electrode film mixture and fabricatedusing a 2:1 graphite-PTFE ratio binder mixture with parallel processingwere evaluated. This was compared to a dry battery anode similar toSample 2 shown in FIG. 5 made using a 94% graphite powder, 3% PTFE andcombined 3% CMC/PCDF loading in the final electrode film mixtures, andfabricated using a 2:1 graphite-PTFE ratio binder mixture. The electrodefilm with a 1.5% PTFE loading showed a measured first cycle efficiencyof 88.7% as shown in FIG. 8A, which is improved from the 87.8% firstcycle efficiency shown by Sample 2. The current optimized first cycleelectrochemical performance of another dry battery anode made with agraphite-PTFE binder mixture used a 1.5% PTFE loading in the finalelectrode film mixture, and was fabricated using a 2:1 graphite-PTFEratio binder mixture. This electrode film had a measured first cycleefficiency of 91.0% as shown in FIG. 8B.

An example of a specific parallel processing scheme is provided in FIG.9. In the lower (as shown) parallel processing path 901 of theembodiment of FIG. 9, a first structural binder 902 and sacrificialactive materials 904 are combined under nondestructive mixing. Thestructural binder 902 may be PTFE, and the sacrificial active material904 may be graphite. The mixed structural binder and sacrificial activematerial form an initial binder mixture 906 that is then jet-milled in ahigh shear, high intensity process to form a binder mixture 908. In theupper (as shown) parallel processing path 910, a bulk active materialmixture 916 is formed by mixing bulk active materials 912 withadditional binders 914. The bulk active material 912 may be graphite.The additional binders 914 may be, for example, PVDF and/or CMC. Thebulk active material mixture 916 is then combined with the bindermixture 908 in a gentle process to form a bulk active material andbinder mixture 918, which is then processed by a low shear jet millingto form an electrode film mixture 920. The low shear jet milling may beperformed at a high feed rate, for example, relative to the initial jetmilling used to form the binder mixture 920. The electrode film mixture920 may then be pressed or calendered into a self-supporting electrodefilm 922. Generally, no solvents are required in any stage of theprocess.

An anode suitable for use in a battery was prepared according to themethod of FIG. 9. The anode was composed of 96% graphite, with thebinders being 2% PTFE, 1% CMC, and 1% PVDF. The binder mixture wasprepared by jet-milling 4% of graphite (relative to the final electrodefilm mixture) with 2% PTFE (the “structural binder” in FIG. 9). Theresulting graphite D₅₀ particle size distribution, which hereconstitutes the total active material in the final electrode filmmixture, is about 9 μm and is shown in FIG. 10. For comparison, FIG. 10also provides the graphite D₅₀ particle size distribution of anelectrode film mixture prepared by a conventional dry electrode processin which all graphite (ie the total active material in the electrodefilm mixture) is jet-milled (“serial process”), which is under 6 μm. Theelectrode film mixture prepared by the parallel process showed only asmall reduction in particle size relative to pristine graphite, whereinpristine graphite is shown to have a D₅₀ particle size distribution ofabout 9.5 μm. Additional data for the two films is provided in Table 1,wherein first cycle efficiency is measured in a lithium-based cellprepared by the methods described previously, and the tensile force ismeasured from 20 mm×150 μm electrode films. Although the first cycleefficiencies of lithium-based cells prepared by the parallel processwith 2% PTFE loadings were measured to be 88.9%±0.3%, additional testingfound a first cycle efficiency of 90.9%±0.1%. Similar results and/orbenefits are anticipated for other active materials that can havesimilar performance-reducing effects as graphite in high shearprocesses.

TABLE 1 Tensile Force First Cycle PTFE Process on Breaking (N)Efficiency (%) 2% Serial 0.65 ± 0.05 85.5 ± 0.8 2% Parallel 1.46 ± 0.0788.9 ± 0.3

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms. Furthermore, various omissions, substitutions and changes in thesystems and methods described herein may be made without departing fromthe spirit of the disclosure. The accompanying claims and theirequivalents are intended to cover such forms or modifications as wouldfall within the scope and spirit of the disclosure. Accordingly, thescope of the present inventions is defined only by reference to theappended claims.

Features, materials, characteristics, or groups described in conjunctionwith a particular aspect, embodiment, or example are to be understood tobe applicable to any other aspect, embodiment or example described inthis section or elsewhere in this specification unless incompatibletherewith. All of the features disclosed in this specification(including any accompanying claims, abstract and drawings), and/or allof the steps of any method or process so disclosed, may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. The protection is notrestricted to the details of any foregoing embodiments. The protectionextends to any novel one, or any novel combination, of the featuresdisclosed in this specification (including any accompanying claims,abstract and drawings), or to any novel one, or any novel combination,of the steps of any method or process so disclosed.

Furthermore, certain features that are described in this disclosure inthe context of separate implementations can also be implemented incombination in a single implementation. Conversely, various featuresthat are described in the context of a single implementation can also beimplemented in multiple implementations separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations, one or more features from a claimedcombination can, in some cases, be excised from the combination, and thecombination may be claimed as a subcombination or variation of a subcombination.

Moreover, while operations may be depicted in the drawings or describedin the specification in a particular order, such operations need not beperformed in the particular order shown or in sequential order, or thatall operations be performed, to achieve desirable results. Otheroperations that are not depicted or described can be incorporated in theexample methods and processes. For example, one or more additionaloperations can be performed before, after, simultaneously, or betweenany of the described operations. Further, the operations may berearranged or reordered in other implementations. Those skilled in theart will appreciate that in some embodiments, the actual steps taken inthe processes illustrated and/or disclosed may differ from those shownin the figures. Depending on the embodiment, certain of the stepsdescribed above may be removed, others may be added. Furthermore, thefeatures and attributes of the specific embodiments disclosed above maybe combined in different ways to form additional embodiments, all ofwhich fall within the scope of the present disclosure. Also, theseparation of various system components in the implementations describedabove should not be understood as requiring such separation in allimplementations, and it should be understood that the describedcomponents and systems can generally be integrated together in a singleproduct or packaged into multiple products. For example, any of thecomponents for an energy storage system described herein can be providedseparately, or integrated together (e.g., packaged together, or attachedtogether) to form an energy storage system.

For purposes of this disclosure, certain aspects, advantages, and novelfeatures are described herein. Not necessarily all such advantages maybe achieved in accordance with any particular embodiment. Thus, forexample, those skilled in the art will recognize that the disclosure maybe embodied or carried out in a manner that achieves one advantage or agroup of advantages as taught herein without necessarily achieving otheradvantages as may be taught or suggested herein.

Conditional language, such as “can,” “could,” “might,” or “may,” unlessspecifically stated otherwise, or otherwise understood within thecontext as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements, and/or steps. Thus, such conditional language is notgenerally intended to imply that features, elements, and/or steps are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or without userinput or prompting, whether these features, elements, and/or steps areincluded or are to be performed in any particular embodiment.

Conjunctive language such as the phrase “at least one of X, Y, and Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to convey that an item, term, etc. may beeither X, Y, or Z. Thus, such conjunctive language is not generallyintended to imply that certain embodiments require the presence of atleast one of X, at least one of Y, and at least one of Z.

Language of degree used herein, such as the terms “approximately,”“about,” “generally,” and “substantially” as used herein represent avalue, amount, or characteristic close to the stated value, amount, orcharacteristic that still performs a desired function or achieves adesired result. For example, the terms “approximately”, “about”,“generally,” and “substantially” may refer to an amount that is withinless than 10% of, within less than 5% of, within less than 1% of, withinless than 0.1% of, and within less than 0.01% of the stated amount,depending on the desired function or desired result.

The scope of the present disclosure is not intended to be limited by thespecific disclosures of preferred embodiments in this section orelsewhere in this specification, and may be defined by claims aspresented in this section or elsewhere in this specification or aspresented in the future. The language of the claims is to be interpretedbroadly based on the language employed in the claims and not limited tothe examples described in the present specification or during theprosecution of the application, which examples are to be construed asnon-exclusive.

What is claimed is:
 1. A parallel processing method for preparing anelectrode film comprising: providing an initial binder mixturecomprising a first binder and a first active material; processing theinitial binder mixture under high shear to form a secondary bindermixture; forming an electrode film mixture by mixing the secondarybinder mixture with a second active material by a first nondestructivemixing process; and forming an electrode film from the electrode filmmixture, wherein the electrode film is a free-standing film.
 2. Themethod of claim 1, wherein mixing the secondary binder mixture with thesecond active material by the first nondestructive mixing processcomprises mixing at least one of a lower pressure, lower velocity, andfaster feed rate than the processing under high shear step.
 3. Themethod of claim 1, wherein the first binder and the first activematerial are mixed by a second nondestructive mixing process to form theinitial binder mixture prior to providing the initial binder mixture. 4.The method of claim 3, wherein at least one of the first and the secondnondestructive mixing processes is an acoustic mixing process.
 5. Themethod of claim 1, wherein mixing comprises mixing the binder mixturewith an active material mixture, the active material mixture comprisingthe second active material.
 6. The method of claim 5, wherein the activematerial mixture further comprises a second binder.
 7. The method ofclaim 1, wherein the mass ratio of the first active material to thefirst binder is between about 1:1 to about 4:1 by weight.
 8. The methodof claim 1, wherein the second active material comprises a treatedsurface.
 9. The method of claim 1, wherein the second active materialwithin the electrode film comprises active material particle surfacesthat are pristine.
 10. The method of claim 9, wherein the combined D₅₀particle size distribution of a total active material, including thefirst and second active materials, in the electrode film mixture is atleast about 6 μm.
 11. The method of claim 1, wherein the electrode filmmixture is not exposed to a high shear process before being formed intothe electrode film.
 12. An electrode film for an energy storage devicecomprising: an active material comprising active material particles,wherein the D₅₀ size distribution of a total of the active materialparticles is at least about 6 μm; and a binder; wherein the electrodefilm is a free-standing film.
 13. The electrode film of claim 12,wherein the electrode film has a tensile strength of greater than about0.25 MPa.
 14. The electrode film of claim 13, wherein the electrode filmhas a tensile strength of about 0.3 MPa to about 0.7 MPa.
 15. Theelectrode film of claim 12, wherein the electrode film comprises a totalbinder loading of about 1.5% to about 4% by mass.
 16. The electrode filmof claim 12, wherein the active material comprises an anode activematerial.
 17. The electrode film of claim 16, wherein the anode activematerial comprises graphite.
 18. The electrode film of claim 12, whereinthe active material comprises sulfur or a material including sulfur. 19.The electrode film of claim 12, wherein the electrode film issubstantially free of solvent residue.
 20. The electrode film of claim12, wherein the second active material within the electrode filmcomprises active material particle surfaces that are pristine.
 21. Anenergy storage device comprising: an anode comprising an electrode film,wherein the electrode film comprises an active material comprisinggraphite, and a binder comprising PTFE; a cathode; a separator; and anelectrolyte; wherein the energy storage device has a first cycleefficiency of greater than about 85%.
 22. The energy storage device ofclaim 21, wherein the energy storage device has a first cycle efficiencyof at least about 90%.
 23. The energy storage device of claim 21,wherein the energy storage device is a battery.
 24. The energy storagedevice of claim 21, wherein the electrode film comprises a total binderloading of about 1.5% to about 4% by mass.
 25. The energy storage deviceof claim 21, wherein the cathode comprises sulfur or a materialincluding sulfur.
 26. The energy storage device of claim 21, wherein theelectrode film is substantially free of solvent residue.
 27. The energystorage device of claim 21, wherein the active material within theelectrode film comprises active material particle surfaces that arepristine.
 28. The energy storage device of claim 27, wherein thecombined D₅₀ particle size distribution of a total of the activematerial is at least about 6 μm.